Peroxynitrite Modulates Release of Inflammatory Mediators from Guinea Pig Lung Mast Cells Activated by Antigen-Antibody Reaction

Bronchioloalveolar lung tumors induced in “mice only” by non-genotoxic chemicals are not useful for quantitative assessment of pulmonary adenocarcinoma risk in humans

Chemicals classified as known human carcinogens by International Agency for Research on Cancer (IARC) show a low level of concordance between rodents and humans for induction of pulmonary carcinoma. Rats and mice exposed via inhalation for 2 years show a low level of concordance in both tumor development and organ site location. In 2-year inhalation studies using rats and mice, when pulmonary tumors are seen in only male or female mice or both, but not in either sex of rat, there is a high probability that the murine pulmonary tumor has been produced via Clara cell or club cell (CC) metabolism of the inhaled chemical to a cytotoxic metabolite. Cytotoxicity-induced mitogenesis increases mutagenesis via amplification of the background mutation rate. If the chemical being tested is also negative in the Ames Salmonella mutagenicity assay, and only mouse pulmonary tumors are induced, the probability that this pulmonary tumor is not relevant to human lung cancer risk goes even higher. Mice have a larger percentage of CCs in their distal airways than rats, and a much larger percentage than in humans. The CCs of mice have a much higher concentration of metabolic enzymes capable of metabolizing xenobiotics than CCs in either rats or humans. A principal threat to validity of extrapolating from the murine model lies in the unique capacity of murine CCs to metabolize a significant spectrum of xenobiotics which in turn produces toxicants not seen in rat or human pulmonary pathophysiology.

Sinapic acid ameliorates bleomycin-induced lung fibrosis in rats

BACKGROUND

Pulmonary fibrosis is a multifaceted disease with high mortality and morbidity, and it is commonly nonresponsive to conventional therapy.

PURPOSE

We explore the possible discourse of sinapic acid (SA) against the prevention of bleomycin (BLM)-instigated lung fibrosis in rats through modulation of Nrf2/HO-1 and NF-κB signaling pathways.

DESIGN/METHODS

Lung fibrosis was persuaded in Sprague-Dawley rats by a single intratracheal BLM (6.5 U/kg) injection. Then, these rats were treated with SA (10 and 20 mg/kg, p.o.) for 28 days. The normal control rats provided saline as a substitute of BLM. The lung function and biochemical, histopathological, and molecular alterations were studied in serum, bronchoalveolar lavage fluid (BALF), and the lungs tissues.

RESULTS

SA treatment significantly restored BLM-induced alterations in body weight index and serum biomarkers [lactate dehydrogenase (LDH) and alkaline phosphatase (ALP)]. SA (10 and 20 mg/kg) treatment appeared to show a pneumoprotective effect through upregulation of antioxidant status, downregulation of inflammatory cytokines and MMP-7 expression, and reduction of collagen accumulation (hydroxyproline). Nrf2, HO-1, and TGF-β expression was downregulated in BLM-induced fibrosis model, while the reduced expression levels were significantly and dose-dependently upregulated by SA (10 and 20 mg/kg) treatment. We demonstrated that SA ameliorates BLM-induced lung injuries through inhibition of apoptosis and induction of Nrf2/HO-1-mediated antioxidant enzymes via NF-κB inhibition. The histopathological findings also revealed that SA treatment (10 and 20 mg/kg) significantly ameliorated BLM-induced lung injury.

CONCLUSION

The present results showed the ability of SA to restore the antioxidant system and to inhibit oxidative stress, proinflammatory cytokines, extracellular matrix, and TGF-β. This is first report demonstrating that SA amoleriates BLM induced lung injuries through inhibition of apoptosis and induction of Nrf2 and HO-1 mediated antioxidant enzyme via NF-κB inhibition. The histopathological finding reveals that SA treatment (10 and 20 mg/kg) significantly ameliorates BLM induced lung injuries.

Acute glutathione depletion leads to enhancement of airway reactivity and inflammation via p38MAPK-iNOS pathway in allergic mice

Glutathione (GSH) plays a major role in allergic airway responses through a variety of mechanism which include direct scavenging of oxidative species, being a reducing equivalent and regulation of cellular signaling through redox sensitive mechanisms. Therefore, the aim of the present study was to evaluate the role of acute GSH depletion on airway reactivity, inflammation and NO signaling in a mouse model of allergic asthma. Buthionine sulfoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase was used for depletion of GSH levels. Acute depletion of GSH with BSO worsened allergen induced airway reactivity and inflammation through increase in nitrosative stress as reflected by increased inducible NO synthase (iNOS) expression, total nitrates and nitrites (NOx), nitrotyrosine, protein carbonyls, and decreased total antioxidant capacity. Treatment with p38 mitogen-activated protein kinase (MAPK) and iNOS inhibitors attenuated the effects of GSH depletion on airway reactivity and inflammation through attenuation of nitrosative stress as evidenced by a decrease in NOx, nitrotyrosine, protein carbonyls and increase in total antioxidant capacity (TAC). In conclusion, these data suggest that acute depletion of glutathione is associated with alteration of airway responses through an increase in nitrosative stress in allergic airways of mice.

Isolation of Rat Lung Mast Cells for Purposes of One-Week Cultivation Using Novel Percoll Variant Percoll PLUS

Prolonged cultivation of separated rat lung mast cells (LMC) in vitro is necessary to better investigate a possible role of LMC in different stages of tissue remodeling induced by hypoxia. Rat lung mast cells (LMC) were separated using a protocol including an improved proteolytic extraction and two subsequent density gradient separations on Ficoll-Paque PLUS and a new generation of Percoll, i.e. Percoll PLUS. Instead of usual isotonic stock Percoll solution, an alternative “asymptotically isotonic” stock solution was more successful in our density separation of LMC on Percoll PLUS. Separated cells were cultivated for six days in media including stem cell factor, interleukins IL-3 and IL-6, and one of two alternative mixtures of antibiotics. These cultivations were performed without any contamination and with only rare changes in cell size and morphology. Model co-cultivation of two allogenic fractions of LMC often caused considerable rapid changes in cell morphology and size. In contrast to these observations no or rare morphological changes were found after cultivation under hypoxic conditions. In conclusions, we modified separation on Percoll PLUS to be widely used, altered LMC separation with respect to purposes of long-lasting cultivation and observed some model morphological changes of LMC.

8-oxo-2'-deoxyguanosine suppresses allergy-induced lung tissue remodeling in mice

We previously reported that 8-oxo-2'-deoxyguanosine (8-oxo-dG) suppressed airway hyperresponsiveness and allergy-associated immune responses in ovalbumin-induced allergic mice by inactivating Rac. In the present study, 8-oxo-dG was investigated for its suppression of inflammation and remodeling in lung tissues induced by allergic reaction in mice. Mice were sensitized and challenged with ovalbumin without or with oral administration of 8-oxo-dG. The mice without 8-oxo-dG administration showed the following inflammatory and airway remodeling signs: infiltration of inflammatory cells into peribronchial area, hyperplasia of mucus-secreting goblet cells in bronchial walls, increase of expressions of Muc5ac and vascular cell adhesion molecule (VCAM)-1, collagen deposition and protein expression, and matrix metalloproteinase (MMP)-2/-9 expressions. We also observed an increase of various inflammation-mediating proteins, namely IL-4, IL-5, IL-8, IL-13, TNF-α and IFN-γ, and activation of STAT1 and NF-κB. Production of reactive oxygen species and nitric oxide (NO(.)) was increased as indicated by a dramatic increase in formation of nitro-tyrosine. Importantly, Rac1 and 2 were also markedly activated. However, 8-oxo-dG suppressed all these inflammatory and tissue remodeling signs as well as activation of Rac1 and 2. These results indicate that 8-oxo-dG can inhibit allergy-induced inflammation and remodeling in airway and lung tissues through Rac inactivation.

Protein tyrosine nitration of aldolase in mast cells: a plausible pathway in nitric oxide-mediated regulation of mast cell function

NO is a short-lived free radical that plays a critical role in the regulation of cellular signaling. Mast cell (MC)-derived NO and exogenous NO regulate MC activities, including the inhibition of MC degranulation. At a molecular level, NO acts to modify protein structure and function through several mechanisms, including protein tyrosine nitration. To begin to elucidate the molecular mechanisms underlying the effects of NO in MCs, we investigated protein tyrosine nitration in human MC lines HMC-1 and LAD2 treated with the NO donor S-nitrosoglutathione. Using two-dimensional gel Western blot analysis with an anti-nitrotyrosine Ab, together with mass spectrometry, we identified aldolase A, an enzyme of the glycolytic pathway, as a target for tyrosine nitration in MCs. The nitration of aldolase A was associated with a reduction in the maximum velocity of aldolase in HMC-1 and LAD2. Nuclear magnetic resonance analysis showed that despite these changes in the activity of a critical enzyme in glycolysis, there was no significant change in total cellular ATP content, although the AMP/ATP ratio was altered. Elevated levels of lactate and pyruvate suggested that S-nitrosoglutathione treatment enhanced glycolysis. Reduced aldolase activity was associated with increased intracellular levels of its substrate, fructose 1,6-bisphosphate. Interestingly, fructose 1,6-bisphosphate inhibited IgE-mediated MC degranulation in LAD2 cells. Thus, for the first time we report evidence of protein tyrosine nitration in human MC lines and identify aldolase A as a prominent target. This posttranslational nitration of aldolase A may be an important pathway that regulates MC phenotype and function.

Signaling pathways in the activation of mast cells cocultured with astrocytes and colocalization of both cells in experimental allergic encephalomyelitis

Mast cells in the CNS participate in the pathophysiology of chronic neurodegenerative inflammatory diseases. This study aimed to investigate the signaling pathway of mast cells activated in an environment cocultured with astrocytes and to explore the role of their colocalization in brain of experimental allergic encephalomyelitis. Human mast cell line-1 cells and human U87 glioblastoma cell lines (U87) or mouse bone marrow-derived mast cells and mouse cerebral cortices-derived astrocytes were cocultured. Intracellular Ca(2+) was measured by confocal microscopy; histamine by fluorometric analyzer; leukotrienes by ELISA; small GTPases, protein kinase Cs, MAPK, c-kit, CD40, and CD40L by Western blot; NF-kappaB and AP-1 by EMSA; cytokines by RT-PCR; and colocalization of mast cells and astrocytes in brain by immunohistochemistry. Mast cells cocultured with astrocytes showed time-dependent increases in intracellular Ca(2+) levels, release of histamine and leukotrienes, and cytokine production. Mast cells or astrocytes showed enhanced surface expression of CD40L and CD40, respectively, during coculture. Mast cells cocultured with astrocytes induced small GTPases (Rac1/2, cdc42), protein kinase Cs, MAPK, NF-kappaB, and AP-1 activities. These changes were blocked by anti-CD40 Ab pretreatment or CD40 small interfering RNA. Mast cells increased in the thalamus of experimental allergic encephalomyelitis model, particularly colocalized with astrocytes in the thalamic border region of the habenula. In conclusion, the data suggest that activation of mast cells cocultured with astrocytes induces release of mediators by small GTPases/Ca(2+) influx through CD40-CD40L interactions to participate in the pathophysiology of chronic neurodegenerative inflammatory diseases, such as multiple sclerosis.

Advances in mast cell biology: new understanding of heterogeneity and function

Mast cells are classically viewed as effector cells of IgE-mediated allergic diseases. However, over the last decade our understanding has been enriched about their roles in host defense, innate and adaptive immune responses, and in homeostatic responses, angiogenesis, wound healing, tissue remodeling, and immunoregulation. Despite impressive progress, there are large gaps in our understanding of their phenotypic heterogeneity, regulatory mechanisms involved, and functional significance. This review summarizes our knowledge of mast cells in innate and acquired immunity, allergic inflammation and tissue homeostasis, as well as some of the regulatory mechanisms that control mast cell development, phenotypic determination, and function, particularly in the context of mucosal surfaces.

Effects of erdosteine on bleomycin-induced lung fibrosis in rats

This study was designed to examine the effects of erdosteine on bleomycin (BLM)-induced lung fibrosis in rats. Thirty-three Sprague-Dawley rats were divided randomly into three groups, bleomycin alone (BLM), bleomycin + erdosteine (BLM + ERD), and saline alone (control). The BLM and BLM + ERD groups, were given 2.5 mg/kg BLM intratracheally. The first dose of oral erdosteine (10 mg/kg/day) in the BLM + ERD group was started 2 days before BLM administration and continued until animals were sacrificed. Animals were sacrificed 14 days after intratracheal instillation of BLM. The effect of erdosteine on pulmonary fibrosis was studied by analysis of bronchoalveolar lavage (BAL) fluid, histopathology, and biochemical measurements of lung tissue superoxide dismutase (SOD) and glutathione (GSH) as antioxidants, malondialdehyde (MDA) as an index for lipid peroxidation, and nitrite/nitrate levels. Bleomycin-induced lung fibrosis as determined by lung histology was prevented with erdosteine (grades of fibrosis were 4.9, 2.3, and 0.2 in BLM, BLM + ERD, and control groups, respectively). Erdosteine also prevented bleomycin-induced increase in MDA (MDA levels were 0.50 +/- 0.15, 0.11 +/- 0.02, and 0.087+/- 0.03 nmol/mg protein in BLM, BLM + ERD, and control groups, respectively) and nitrite/nitrate (nitrite/nitrate levels were 0.92 +/- 0.06, 0.60 +/- 0.09, and 0.56+/- 0.1 micromol/mg protein in BLM, BLM + ERD, and control groups respectively) levels. Bleomycin-induced decrease in GSH and SOD levels in the lung tissue also prevented by erdosteine [(GSH levels were 213.5 +/- 12.4, 253.2+/- 25.2, and 287.9+/- 34.4 nmol/mg protein) (SOD levels were 1.42+/- 0.12, 1.75+/- 0.17, and 1.89+/- 0.09 U/mg protein) in BLM, BLM + ERD, and control groups respectively]. Erdosteine prevented bleomycin-induced increases in total cell number and neutrophil content of the BAL fluid. In conclusion, oral erdosteine is effective in prevention of BLM-induced lung fibrosis in rats possibly via the repression of neutrophil accumulation, inhibition of lipid peroxidation, and maintenance of antioxidant and free radical scavenger properties.

The acute and chronic phases of chronic relapsing experimental autoimmune encephalomyelitis (CR EAE) are ameliorated by the peroxynitrite decomposition catalyst, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinatoiron (III) chloride, (FeTPPS)

There is increasing evidence that the oxidative radical, peroxynitrite (ONOO(-)), is involved in the pathogenesis of inflammatory diseases including multiple sclerosis and the animal counterpart, experimental autoimmune encephalomyelitis (EAE). Compounds that impede the actions of ONOO(-) have proved useful in the control of EAE. In particular, catalytic isomerisation of ONOO(-) to inactive nitrate, through the use of metalloporphyrins, curtails the cellular response to inflammatory stimuli and halts the progression of neuroinflammation during EAE. The present study examined the pharmacological effects of the metalloporphyrin and ONOO(-) decomposition catalyst 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinatoiron(III)chloride (FeTPPS) on the acute and relapse phases of chronic relapsing (CR) EAE. Administration of FeTPPS to CR EAE-inoculated Biozzi mice commenced either therapeutically and immediately prior to the emergence of acute or relapse symptoms, or prophylactically, from the onset of remission of acute neurological signs. Drug therapy reduced acute and relapse symptoms but, and in contrast to the former phase, was of limited benefit in preventing histological changes during the latter stage of disease. In contrast, prophylactic FeTPPS was effective in limiting CNS pathology and neurological deficits. The findings confirm the inhibitory effects of FeTPPS on acute stage EAE. Moreover, the study extends previous observations by verifying compound efficacy on relapsing disease. Use of metalloporphyrins, such as FeTPPS, again highlights the important role played by ONOO(-) in the development of inflammatory diseases such as EAE.

Rapid non-genomic effects of glucocorticoids on oxidative stress in a guinea pig model of asthma

BACKGROUND AND OBJECTIVE

Glucocorticoids (GC) may exert therapeutic effects in asthma by a rapid non-genomic mechanism. The lungs of asthmatic patients are exposed to oxidative stress, which is believed to be critical in the pathogenesis of asthma. The aim of this study was to investigate whether GC exert a rapid non-genomic effect on oxidative stress in asthmatic guinea pigs.

METHODS

The guinea pig asthma model was used to assess inhibitory effects of budesonide (BUD) on oxidative stress. BAL fluid (BALF), trolox equivalent antioxidant capacity and lung manganese superoxide dismutase (MnSOD) activity were measured by spectrophotometry. Superoxide anion production was measured by cytochrome c reduction assay.

RESULTS

Oxidative stress occurred within minutes following antigen challenge and BUD reduced the severity of oxidative stress in asthmatic guinea pigs within 15 min. BUD significantly decreased BALF trolox equivalent antioxidant capacity and lung MnSOD activity, as compared with those of vehicle-treated asthmatic guinea pigs (P < 0.05). Additionally, BUD rapidly inhibited in vitro superoxide anion production by BALF cells and bronchi harvested from sensitized animals. These rapid effects were not blocked by the GC receptor antagonist RU486 and/or the protein synthesis inhibitor cycloheximide.

CONCLUSIONS

BUD reduced oxidative stress in a guinea pig model of asthma by a rapid non-genomic mechanism. These data suggest new mechanisms whereby GC treatments may benefit asthma.

Hyaluronic acid targets CD44 and inhibits FcepsilonRI signaling involving PKCdelta, Rac1, ROS, and MAPK to exert anti-allergic effect

Effects of hyaluronic acid (HA) on allergic inflammation were investigated. HA exerted negative effects on beta-hexoaminidase secretion and histamine release in antigen-stimulated rat basophilic leukemia (RBL2H3) cells. HA inhibited interaction between IgE and FcepsilonRI and between FcepsilonRI and PKCdelta. HA inhibited CD44 interaction with PKCalpha, indicating that HA targets CD44. PKCalpha and -delta were responsible for increased Rac1 activity and expression of p47(phox), p67(phox). HA inhibited phosphorylation of PKCalpha and -delta. Rac1 was responsible for increased ROS, and NADPH oxidase was the main source for ROS. The inhibition of PKC prevented antigen from increasing phosphorylation of ERK and p38 MAPK. ERK, p38 MAPK, and ROS, were responsible for secretion of beta-hexosaminidase, histamine release, and induction of chemokines. HA suppressed induction of chemokines, such as MIP-2 and Sprr-2a. CD44 mediated effect of antigen on phosphorylation of ERK, p38MAPK, ROS production, secretion of beta-hexosaminidase, and histamine release. GPCR did not mediate allergic function of antigen or affect anti-allergic function of HA. In vivo anti-allergic effect of HA was investigated using Nc/Nga mice model of DNFB-induced atopic dermatitis. HA reduced skin lesions in Nc/Nga mice treated with DNFB, decreased expression levels of MIP-2, Sprr-2a, and serum IgE level. In conclusion, hyaluronic acid exerts negative effect on allergic inflammation by targeting CD44 and inhibiting FcepsilonRI signaling.

Peroxynitrite: biochemistry, pathophysiology and development of therapeutics

Peroxynitrite--the product of the diffusion-controlled reaction of nitric oxide with superoxide radical--is a short-lived oxidant species that is a potent inducer of cell death. Conditions in which the reaction products of peroxynitrite have been detected and in which pharmacological inhibition of its formation or its decomposition have been shown to be of benefit include vascular diseases, ischaemia-reperfusion injury, circulatory shock, inflammation, pain and neurodegeneration. In this Review, we first discuss the biochemistry and pathophysiology of peroxynitrite and then focus on pharmacological strategies to attenuate the toxic effects of peroxynitrite. These include its catalytic reduction to nitrite and its isomerization to nitrate by metalloporphyrins, which have led to potential candidates for drug development for cardiovascular, inflammatory and neurodegenerative diseases.

Modulation of the effects of chylomicron remnants on endothelial function by minor dietary lipid components

There is emerging evidence that minor components from dietary oils can modulate or even improve events occurring in the development of atherosclerosis. One of the earliest events of the atherosclerotic process is endothelial dysfunction, which is an activation of the endothelium manifested by an increase in pro-inflammatory molecules, such as cytokines and adhesion molecules. Chylomicron remnants, such as LDL (low-density lipoprotein), are considered to be pro-atherogenic lipoproteins because they interact with endothelial cells and macrophages, increasing endothelial dysfunction mainly by the disturbance of the redox state in the cell. However, chylomicrons are, at the same time, the natural carriers of dietary lipids in plasma, which gives minor lipid components the opportunity to interact with the cells implicated in endothelial dysfunction and atherogenesis. Some of these components are known to exhibit antioxidant, anti-inflammatory and anti-atherogenic effects in vitro, even forming part of triacylglycerol-rich lipoproteins, such as chylomicrons.

Modulation of inflammation in brain: a matter of fat

Neuroinflammation is a host defense mechanism associated with neutralization of an insult and restoration of normal structure and function of brain. Neuroinflammation is a hallmark of all major CNS diseases. The main mediators of neuroinflammation are microglial cells. These cells are activated during a CNS injury. Microglial cells initiate a rapid response that involves cell migration, proliferation, release of cytokines/chemokines and trophic and/or toxic effects. Cytokines/chemokines stimulate phospholipases A2 and cyclooxygenases. This results in breakdown of membrane glycerophospholipids with the release of arachidonic acid (AA) and docosahexaenoic acid (DHA). Oxidation of AA produces pro-inflammatory prostaglandins, leukotrienes, and thromboxanes. One of the lyso-glycerophospholipids, the other products of reactions catalyzed by phospholipase A2, is used for the synthesis of pro-inflammatory platelet-activating factor. These pro-inflammatory mediators intensify neuroinflammation. Lipoxin, an oxidized product of AA through 5-lipoxygenase, is involved in the resolution of inflammation and is anti-inflammatory. Docosahexaenoic acid is metabolized to resolvins and neuroprotectins. These lipid mediators inhibit the generation of prostaglandins, leukotrienes, and thromboxanes. Levels of prostaglandins, leukotrienes, and thromboxanes are markedly increased in acute neural trauma and neurodegenerative diseases. Docosahexaenoic acid and its lipid mediators prevent neuroinflammation by inhibiting transcription factor NFkappaB, preventing cytokine secretion, blocking the synthesis of prostaglandins, leukotrienes, and thromboxanes, and modulating leukocyte trafficking. Depending on its timing and magnitude in brain tissue, inflammation serves multiple purposes. It is involved in the protection of uninjured neurons and removal of degenerating neuronal debris and also in assisting repair and recovery processes. The dietary ratio of AA to DHA may affect neurodegeneration associated with acute neural trauma and neurodegenerative diseases. The dietary intake of docosahexaenoic acid offers the possibility of counter-balancing the harmful effects of high levels of AA-derived pro-inflammatory lipid mediators.